FIG. 1 shows a schematic circuit diagram showing a standard heating operation of a heat pump according to a conventional practice (which is disclosed in Korean Patent Registration No. 10-0965057 entitled ‘heat pump’ as filed by the same applicant as this invention, wherein the heat pump 10 includes a compressor 200, a four-way valve 210, an indoor unit 220, check valves 240, expansion valves 230, a three-way valve 250, an outdoor unit main coil 90, an outdoor unit auxiliary coil 100, an outdoor unit blower 110, and an accumulator 270.
As shown in FIG. 1, under the standard heating conditions (having the air of more than 5° C. in the outdoor unit) where no frost is formed, the outdoor unit main coil 90 and the outdoor unit auxiliary coil 100 are all operated as an evaporator to optimize the evaporating capability, thereby improving the performance of the heat pump.
FIG. 2 shows a schematic circuit diagram showing defrosting and heating operations of the heat pump according to the conventional practice under the outdoor air conditions where frost is formed. In the state where the outdoor air has a high humidity and a temperature in a range between −2° C. and 2° C., if the outdoor unit auxiliary coil 100 is operated as the condenser so as to suppress or delay the frosting on the outdoor unit coils during the heating operation of the heat pump, the outdoor air becomes warm via the outdoor unit auxiliary coil 100 and the warm air is then passed through the outdoor unit main coil 90, such that the frosting on the outdoor unit main coil 90 can be delayed or suppressed.
However, if high temperature and high pressure refrigerant flow, which is emitted from the compressor 200 and introduced to the outdoor unit auxiliary coil 100, is low, the air passed through the outdoor unit auxiliary coil 100 cannot be sufficiently heated, thereby failing to obtain perfect defrosting effects. Contrarily, if the refrigerant flow introduced to the outdoor unit auxiliary coil 100 is high, the formation of the frost can be suppressed or delayed for a long period of time, but an amount of refrigerant flowing toward the indoor unit 220 for a heating operation becomes reduced to provide poor heating capability.
So as to solve the above-mentioned problems conflicting with each other, there is a need for the development of a method and device that produces an optimal amount of refrigerant satisfying both of heating capability (COP: coefficient of performance) of a heating pump and a delay time period in the formation of frost as user's desired levels and that accurately distributes the amount of refrigerant to the outdoor unit auxiliary coil 100 and the indoor unit 220. However, it is difficult to find such method and device from the products used in practice.